1. Field of the Disclosure
The disclosure relates to a touch display panel, and more particularly to a touch display panel with capacitive light-sensing structure.
2. Description of Related Art
In currently various consumer electronics products, many portable electronics products, such as a personal digital assistant (PDA), a mobile phone, and a notebook, personal computers, and digital home appliance systems employ touch display panels to serve as interface tool between users and the electronics products. When using a touch display panel, users can perform operation and issue commands directly through objects shown on the panel, which allows batter human operation interface. Currently, electronics products are developed toward light, thin, short, and small design. Thus, it is desired to save the space occupied to dispose conventional input devices, such as buttons, keyboards, and mice in design of electronics products. A display device with a touch display panel becomes one of critical components of various electronics products.
According to structure characteristics, touch display panels are divided into on-cell touch display panels and in-cell touch display panels. An on-cell touch display panel comprises not only a display panel but also a touch panel disposed on the display panel, so that while users watch images displayed on the display panel, the touch panel can detect the locations touched by the users. An in-cell touch display panel integrates a touch function into a conventional display panel, and, thus, a panel has an input function and an output function. The operation interface of an in-cell display touch is more instinctive than that of an on-cell display touch panel. Further, since an in-cell display panel does not require an additional touch layer, compared with an on-cell display panel, the in-cell display panel has provides batter display quality, low power consumption, and short and thin size, which is current development trend of touch display panel.
In conventional in-cell touch display panel technique, a sensing element, such as a light-sensing element, is integrated into a thin film transistor (TFT) array. In other words, a sensing element and conventional TFTs are integrated into one pixel. By different driving signals and detection signals, a display function and a touch detection function can be accomplished in one pixel. Generally, a light sensing element uses a characteristic of that a semiconductor material (such as amorphous silicon) generates photo-charges after illuminated by light, and a touch location can be detected by detecting the generation of the photo-current. A conventional light-sensing element comprises a amorphous silicon TFT or a P-inrtinsic-n (PIN) photodiode, wherein both of the amorphous silicon TFT and the P-inrtinsic-n (PIN) photodiode can be successfully integrated into current liquid crystal display panels. However, there are some drawbacks about the integration. For example, when a light-sensing element is formed based on the structure of a amorphous silicon TFT, since the amorphous silicon TFT is exposed to light for a long time, the photoelectric effect of the amorphous silicon material declines gradually, which results degradation of the capability of sensing light. When a light-sensing element based on the structure of a PIN photodiode, since the polycrystalline silicon has worse light-absorbing efficiency, the detection sensitivity is not desirable in the environment with insufficient light.